Metal extrusion press and method of operation



Feb. 8, 1938. R. w. ATKINSON .1

METAL EXTRUSION PRESS AND METHOD OF OPERATION Filed Dec. 18, 1933 2Sheets-Sheet l 1 r HI lllll- I m I MU W INVENTOR Ra/ofi W/W/hJO/ YATTORNEYS Feb. 8, 1938. R. w. ATKINSON METAL EXTRU SION PRESS AND METHODOF OPERATION Filed Dec. 1a, 1953 .2 ShQetS Sheet 2 YNVENTOR amx at .E nm A M KQ m M Patented Feb. 8, 1938 UNITED STATES,

PATENT OFFICE EXTRUSION PRESS AND METHOD OF OPERATION ApplicationDecember 18, 1933, Serial No. 702,872

11 Claims.

This invention relates to metal extrusion presses and the method ofoperating such presses. More particularly the invention is concernedwith presses for extruding metal sheaths on electrical cables.Ordinarily, cable sheaths are made of lead or an alloy of lead. It is anobject of this invention to provide improved apparatus for extrudingmetal, and also to provide an improved method of operating suchapparatus in which the metal to be extruded is not exposed to air orother gases. Other objects and advantages of the invention will appearhereinafter.

The invention will be best understood from the following descriptionwhen read in the light of the accompanying drawings illustrating acertain specific embodiment of the invention.

In the drawings:

Fig. l is an elevation of a press for extruding cable sheaths and of thecontainer for supplying a molten metal to the press;

' Fig. 2 is a top plan view to enlarged scale of the stuffing box whichconnects the upper end of the press cylinder and the press ram;

Fig. 3 is a vertical section through the stuffing box substantially onthe line 3--3 of Fig. 2;.

Fig. 4 is a vertical section through the stuffing box substantially onthe line 4-4 of Fig. 2; and

Fig. 5 is a section through one of the openings in the stufiing box Wallsubstantially on the line 30 5-5 of Fig. l, but to the same scale asFigs. 2

In sheathing electrical cables with metal there are two types ofvertical presses in general use. In one of these the press cylinder isstationary and the press rarn moves, while in the other the press ram isstationary and the press cylinder moves. The present invention may beused with both types of presses, but merely for convenience it isillustrated herein with reference to a press in m which the cylinder isstationary.

The actual extrusion of metal is not continuous in either type of pressfor the reason that it is necessary to separate the ram and the cylinderand recharge the cylinder with metal when a majority of the originalcharge of metal has been extruded from the cylinder. In recharging, thecylinder is filled with molten metal, and then it is necessary to waituntil the metal cools sufficiently to solidify before the extrusionoperation can be continued.

Heretofore it has been the common practice in charging a press cylinderto separate the cylinder and the ram, and then to fill the cylinder withmolten metal from a nearby melting pot by 55 opening a valve at thebottom of the pot and permitting metal to flow down an inclined trough,the lower end of which has been moved over the open end of the presscylinder. When the cylinder has been filled with molten metal the valveat the bottom of the pot is closed, and 5 an effort is made to removethe dross on the top surface of the metal in the cylinder either byflotation or by skimming. The ram is moved downwardly to seal the chargeand then it is necessary to suspend operations until the molten 10 metalin the press cylinder has solidified. After solidification of the chargethe extrusion operation may be continued.

in operating presses as described above, impurities are accumulated byor formed in the molten metal, and also on the exposed surface of thehot metal slug remaining in the cylinder, and on the thin layers of hotmetal on the surfaces of the cylinder and ram. Exposure of the moltenmetal to the air as it issues from the melting pot 2G and flows throughthe trough to the press cylinder is accompanied by oxidation of themetal. This oxidation results in the formation of dross which is carriedinto the press cylinder. The upper surface of the slug left in thecylinder at the completion of an extrusion operation also begins tooxidize as soon as the ram leaves it on its up-travel. Likewise the thinfilm of metal on the inner surface of the cylinder and the end of theram oxidizes and finds its way into the charge. This oxidized film tendsto prevent perfect welding of the new charge, and while a portion of theoxide may float to the top and be skimmed off, a part of it will remainin the charge. This oxide may reduce the strength of the bond in thecable sheath. Furthermore, some metal may cling to the trough at the completion of a charging operation. Such metal will oxidize in the air andbuild up into large particle sizes which will be carried, possibly withother dirt, into the cylinder with the molten metal during the nextcharging operation.

In charging a press in the manner just described the metal which runsinto the cylinder strikes the relatively cold wall of the cylinder andfreezes in an irregular lump. The surface of this lump films overinstantly and is continuously spattered with more hot metal, forming alarger lump containing oxide and gas bubbles which eventually mustappear in the cable sheath. These entrapped air or gas pockets arecompressed to very small size during the extrusion operation, and expandagain after passing out of the die. If the pocket is near the surface ofthe sheath it will explode outwardly and perhaps may be discovered andrepaired, but it is just as likely that the pocket will occur adjacentthe inner surface of the sheath and burst inwardly, to the detriment ofthe cable insulation, as well as the sheath. These pockets weaken thesheath mechanically, even if they do not burst.

According to the present invention a commercially practicable method andapparatus is provided for extruding cable sheaths, in which oxidation ofthe slug remaining in the cylinder prior to a charging operation isprevented, and in which molten metal passes from the melting pot orother container to the press cylinder without exposure to the air or anyother gas at any point during its movement. Fwthermore, the innersurfaces of the cylinder and lower end of the ram, both of which come incontact with the metal, are not exposed to the air or other aretherefore free from oxides.

R ferring first to 1, extending upwardly cm the base 23 are the verticalcolumns 2i, four number, which support near their upper ends presscanopy comprising the hydraulic r .c. Vertically movable within the cylr.3 is the hydraulic piston 24. Secured on lower e -d of the hydraulicpiston as by cans of the SClLWS 25', is the downwardly exte g press ram26. The press ram passes downwarly through the stuiifing box 2?, to bedescribed more fully hereinafter, into the upper end of the presscylinder 33.

The press cylinder 23 is secured on top of the die block 25, having ahorizontal die opening 33 rough which the cable passes during thesheathng operation. The die blocir rests on the base lovement or" thepress ram into and out of the ress cylinder for the purpose of extrudingmetal herefrom is accomplished by means of the hydraulic cylinder andpiston in the usual manner.

Surrounding the press ram 26 and secured to the upper end of the presscylinder 33, as by means of the screws 32 is the stumng box 2?.Connected in an opening through the wall of the stuffing box is a pipe33 through which the press cylinder is charged with molten metal. Thepipe conveniently is connected, as by means of pipe flanges and the pipe34, with the outlet pipe 35 of a container 38 for molten metal, forexample the melting pot. Conveniently an expansion joint, (not shown)may be included in this pipe connection. Flow of molten metal from thecontainer 33 through the pipes 35, 34 and 33 to the press cylinder 23conveniently may be controlled by means of a valve, (not shown) locatedwithin the container 36 and operated by the valve stem 3'! extendingupwardly through the top of the container 36. The pipes 33, 34 and 35may be covered with heat insulating material if desired.

The construction of the stuffing box 21 is shown more clearly in Figs. 2to 5 inclusive. Conveniently the stuifing box is formed in two pieces 38and 39 which are connected together in posi tion about the press ram bymeans of the screws 43 passing through openings in the outwardlyextending flanges H. A gas-tight connection between the two parts of thestufling box is obtained by means of the gaskets 42, for exampleasbestos, compressed between the flanged edges 4i.

Between the upper end of the press cylinder 28 and the lower edge of thestufling box 2! is a. packing ring 43, which is compressed as the screws32 are turned down to secure the stufling box in position on the upperend of the cylinder. The

box is shown in Fig. 3.

packing 43, for example asbestos, insures gastight connection betweenthe press cylinder and the stufhng box.

The opening 46 in the top of the stuffing box preferably has a slidingfit with the press ram 225. This opening 46 is enlarged near the outersurface of the stuihng box to receive a packing ring ll, for exampleasbestos, which may be compressed by means of the pacln'ng gland 48 andthe screws 49 securing the packing gland to the stufilng box 21'. Forconvenience in assembling, the packing gland may be made in two pieces,as shown in Fig. 2, and when it is forced downwardly by means of thescrews 49 the packing ring ll will be pressed against the surface of therain '18, forming a seal to prevent passage of air or other gas into thepress cylinder between the press ram and the stuffing box.

As may be seen in Figs. 3 and 4, the lower edge of that portion of thestuiilng box having a sliding fit with the press ram preferably is inthe form of a scraping edge 56. As the ram is withdrawn from thecylinder at the conclusion of an extruding operation this edge willscrape from the stu face of the ram any metal which may have escapedpast the end of the ram during the extruding operation.

The metal so removed from the ram will collect within the stufling box21, and preferablymeans are provided for melting this metal so that itmay return to the press cylinder while the cylinder is being chargedwith molten metal. This heating means conveniently may take the form ofan electrical heating unit 53 located within the stuffing box, andpreferably separated from the lower inner wall of the stuffing box byspace or by thermal insulation so as to minimize the heat lost by theunit 53 by conduction. Ordinarily the amount of metal escaping past theend of the ram during an extruding operation is small, and it will notbe necessary to melt the metal accumulated within the stuifing box eachtime that the press cylinder is charged with molten metal.

The connection of the pipe 33 to the stuifing It will be apparent thatmolten metal entering the stufiing box through the pipe 33 will continuedown the inclined chute 56 formed in the inner surface of thestuffing'box and be discharged into the press cylinder 28. During thecharging operation the press ram 26 is Withdrawn from the press cylinderas shown in broken lines in Fig. 3.

Throughout the charging and extruding operations the press cylinder andthe stuffing box desirably are evacuated. Connecting with the interiorof the stuffing box through an opening in the wall thereof is a pipe 58connected, for example through a valve H, to a vacuum pump, indicateddiagrammatically at 12. Desirably, a very high vacuum is maintained sothat the interior of the press cylinder and the stuffing box aresubstantially free from air and other gases which might cause dross toform, or which might be included in the molten metal in the form of gaspockets.

Conveniently means are provided for observing the level of the moltenmetal as it nears the top of the press cylinder during a chargingoperation. As shown in the illustrative embodiment such means may takethe form of oppositely disposed windows BI and 62.

The cross section through one of the windows shown in Fig. 5 illustratesthe construction more fully. The window opening in the wall of the llllIII

. stufiing box is provided with a removable rim 64 held in place bymeans of screws 65 and the wing nuts 66. Mounted in the rim 64 is athick pane 01' glass 61, conveniently held therein along with the gasket$8 by means of the ring 69 secured to the rim M with screws ill. As thering 64 is tightened in place by screwing down the wing nuts 8% thegasket 68 provides a gas-tight seal between the stuffing box 2'? and theglass 61.

The operation of the extruding apparatus will now be described. Upon thecompletion of an extruding operation the press ram 26 is withdrawnupwardly from the press cylinder 28 until the lower end of the ram iscompletely clear of the cylinder as shown in broken lines in Fig. 3. Asthe ram is withdrawn from the cylinder any metal which may have escapedpast the end of the ram during the preceding extruding operation, isscraped from the wall of the ram by the scraping edge 56, and collectsinside of the stuifing box 2?, without injury to the packing ring 4i". 7

The valve controlling the flow of molten metal from the container 35through the pipes 35, 3d and 33 is then opened to permit molten metal toflow from the container 36 into the press cylinder. If the amount ofmetal scraped from the wall of the ram and collected within the stufiingbox is sufiiciently great the electrical heating units 53 may beoperated to melt this metal so that it will flow down the inclined innerwall of the stufiing box into the press cylinder.

As the level of metal in the press cylinder approaches the top of thecylinder it may be observed through the windows 6! and B2, and when themetal reaches the desired level the valve may be closed to stop furtherflow. The charge may then be sealed, and when it has solidified themetal may be extruded by downward movement of the press ram.

Throughout the charging and extruding operations the space within thestufiing box 2'I and within the press cylinder desirably is evacuatedthrough the pipe connection 58. No air or other gases are present, orcome in contact with the metal from the time the molten metal leaves thecontainer 36 until the solidified metal is extruded from the opening 30in the die block 29. Consequently there can be no oxidation or otherdross formation in the metal, and the formation of gas pockets orbubbles in the press cylinder is prevented.

Instead of maintaining a high vacuum in the space within the stufiingbox and the press cylinder during the charging operation it maybedesirable in some cases to introduce into this space steam or someliquid which is inert chemically with respect to the metal beingextruded, and which is a vapor at the temperature of the press cylinderand at atmospheric pressure, but which may be liquefied at the meltingpoint of the extruded metal. other inert material may be supplied to thepress cylinder through the pipe 58, connected, for ex ample through avalve 13, with a source of the inert material indicated diagrammaticallyat I4.

Steam not only is inert chemically with respect to lead, but steam is avapor at the temperature of the cylinder and atmospheric pressure, andyet is liquefied by a reasonable pressure at any temperature that isreached by the cable sheath. If a bubble of permanent gas or very lowboiling liquid be compressed within the mass of the lead during theextruding operation the bubble may expand substantially to its originalvolume after Conveniently, the steam or extrusion, with the harmfulconsequences set forth hereinabove. In the case of steam, however, thecompression within the cylinder will produce a liquid, with a vastreduction in volume, and expansion to gaseous form is prevented by arelative moderate pressure even at the temperature of the lead as it isbeing extruded. The comparatively small volume of the space in which theliquid will be found will result in the lead surrounding it havingsufiicient strength to maintain the liquid in its original volumewithout ex pansion to vapor form, even at the extruding temperature.

Applicant has provided improved apparatus whereby metal sheaths may beextruded about electrical cables, and in which oxidation of the metalduring the extruding operation is prevented. Furthermore, introductionof impurities and formation of gas pockets in the metal dining the presscharging operation is prevented.

It will be understood that the present invention may be variouslymodified and embodied within the scope of the subjoined claims.

I claim:

1. In apparatus for extruding metal sheaths on electrical cables thecombination of a cylinder, a die block having an opening for the passageof a cable therethrou'gh connected to one end of said cylinder, 9. ramextending into the other end of said cylinder, means for causingrelative movement between the cylinder and the ram, sealing meansconnecting the cylinder and the ram preventing the entrance of air intothe cylinder around the ram while permitting relative movementtherebetween, and means for removing substantially all air and othergases from the space between the cylinder and the ram under the saidsealing means.

\ 2. In apparatus for extruding metal sheaths on electrical cables thecombination of a cylinder, a die block having an opening for the passageof a cable therethrough connected to one end of said cylinder, a ramextending into the other end of said cylinder, means for causingrelative movement between the cylinder and the ram, sealing meansconnecting the cylinder and the ram preventing the entrance of air intothe cylinder around the ram while permitting relative movementtherebetween, and an acute angled scraping edge closely encircling theram below the sealing means for removing any metal which may have beenforced out between the cylinder wall and the head of the ram during anextruding operation from the surface of the ram and for directing themetal away from the ram as the latter is I withdrawn from the cylinder.

3. In apparatus for extruding metal sheaths on electrical cables thecombination of a cylinder, 2. die block having an opening for thepassage of a cable therethrough connected to one end of said cylinder,9. ram extending into the other end of said cylinder, means for causingrelative movement between the cylinder and the ram, sealing meansconnecting the cylinder and the ram preventing the entrance of air intothe cylinder around the ram while permitting relative movementtherebetween, a scraping edge closely encircling the ram below thesealing means, for

removing any metal which may have been forced.

out between the cylinder wall and the head of the ram during anextruding operation from the surface of the ram as the latter iswithdrawn from the cylinder, and means for melting any such metal andcausing it to return to the cylinder during a charging operation.

4. In apparatus for extruding metal sheaths on electrical cables thecombination of a cylinder, a die block having an opening for the passageof a cable therethrough connected toone end of said cylinder, 2. ramextending into the other end of said cylinder, means for causingrelative movement between the cylinder and the ram, means for chargingthe cylinder with molten metal, and means for removing substantially allair and other gases from the cylinder during a charging operation.

5. In apparatus for extruding metal sheaths on electrical cables thecombination of a cylinder, 9. die block having an opening for thepassage of a cable therethrough connected to one end of said cylinder, aram extending into the other end of said cylinder, means for causingrelative movement between the cylinder and the ram, means for chargingthe cylinder with molten metal, and means for supplying steam to thecylinder during a charging operation.

6. The method of operating apparatus for extruding metal sheaths onelectrical cables, comprising a cylinder, die block and ram, whichmethod comprises charging the cylinder with molten metal free fromimpurities, permitting the molten metal to cool and solidify, preventingaccess of air to the molten metal during the charging and coolingoperations, removing from the cylinder during the charging operation anygas which may have been entrained in the molten metal, and effectingrelative movement between the cylinder and the ram to extrude thesolidified metal through the die block.

7. The method of operating apparatus for extruding metal sheaths onelectrical cables comprising a cylinder, die block and ram, which methodcomprises charging the cylinder with molten metal free from impurities,permitting the molten metal to cool and solidify, preventing access ofair to the molten metal during the charging operation by maintaining ablanket of steam over the metal in the cylinder, and eilecting relativemovement between the cylinder and the rain to extrude the solidifiedmetal through the die block.

8. In an apparatus for charging an extrusion press cylinder having acooperating ram nor mally retirable from the cylinder to permit chargingof the same through the ram entrance aperture thereof, a receptaclenormally empty of fused material supported upon the cylinder and havingan aperture in the bottom thereof provided with a beveled edge forproviding an entrance into the cylinder and aligned with the ramentrance aperture of the cylinder, said receptacle constituting a sealbetween the cylinder and the rain to exclude the atmosphere from thecylinder, and means for charging the cylinder with fused materialthrough the wall of the receptacle.

9. In apparatus for extruding metal sheaths on electrical cables thecombination of a cylinder, a die block having an opening for the passageof a cable therethrough connected to one end of said cylinder, a ramextending into the other end of said cylinder, means for causingrelative movement between the cylinder and the ram, an annular casingsurrounding the ram and connected fluid tight to the end of thecylinder, a packing secured in the wall of the annular casing encirclingthe ram and preventing entrance of air into the cylinder around the ramwhile permitting relative movement therebetween, and means connected tosaid annular casing for removing substantially all air and other gasesfrom the space between the cylinder and the ram and under the annularcasing.

10. In apparatus for extruding metal sheaths on electrical cables thecombination of a cylinder. a die block having an opening for the passageof a cable therethrough connected to one end of said cylinder, a ramextending into the other end of said cylinder, means for causingrelative movement between the cylinder and the ram, sealing meansconnecting the cylinder and the ram preventing the entrance of air intothe cylinder around the ram while permitting relative move- I menttherebetween, and an acute angled scraper between said sealing means andthe head of the ram for removing any metal which may have been forcedout between the cylinder wall and the head of the ram during anextruding operation from the surface of the ram and for directing themetal away from the ram as the latter is withdrawn from the cylinder.

11. In apparatus for extruding metal sheaths on electrical cables thecombination of a cylinder, a die block having an opening for the passage0! a cable therethrough connected to one end of said cylinder, a ramextending into the other end of said cylinder, means for causingrelative movement between the cylinder and the ram, sealing meansconnecting the cylinder and the ram preventing the entrance of air intothe cylinder around the ram while permitting relative movementtherebetween, means beween said sealing means and the head of the ramfor removing any metal which may have been forced out between thecylinder wall and the head of the ram during an extruding operation fromthe surface of the ram as the latter is withdrawn from the cylinder, andan electrical heating element for melting any such metal and causing itto return to the cylinder during a charging operation.

RALPH W. ATKINSON.

